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Cruise control cancelled through small bump. Several times.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by R-P, Jan 3, 2015.

  1. R-P

    R-P Active Member

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    Tried searching but did not (yet) find this discussed.

    Anyone have a solution or clues as to what's going on? The wife mentioned this happening to her yesterday (she rarely drives the Prius) and I had it happen twice today as well...

    Just a minor bump at 60-70mph and without warning the car would slow down. I haven't observed the skiddinglight flashing when it happened, but I can imagine that might be the cause (summer tires in 2-5 C temperatures (~35-40F) and wet conditions).

    Pushing the 'restore' or whatchamacallit button (push stalk upwards) would let it accelerate to the old set speed, so it is not 'forgetting' its settings, just 'releasing' the cruise control.
     
    #1 R-P, Jan 3, 2015
  2. JC91006

    JC91006 Senior Member

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    If your car loses traction, cruise will cancel. It would only make sense for this to occur
     
    #2 JC91006, Jan 3, 2015
  3. R-P

    R-P Active Member

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    I always feel (even at normal 20+C temps) like I am driving on ice in the wet (every bump taken with some speed causes the traction control to interfere, causing me to loose control of the car: the car decides if it feels like braking, I have no say whatsoever in this, pretty scary feeling), but this is really starting to take a turn for the worse if this is also traction/skid control related...

    I would have to look up which tires I have, but they were at least "very good" in the wet or I would not have chosen them.

    The fact this is occuring quite suddenly makes me not quite convinced it is traction related. I will obviously look out for the orange skidding light and may try to invoke this behaviour if I can find a safe spot to test.
     
    #3 R-P, Jan 3, 2015
  4. JC91006

    JC91006 Senior Member

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    Test and post back. It would be nice to know for sure
     
    #4 JC91006, Jan 3, 2015
  5. bisco

    bisco cookie crumbler

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    it does sound like the tyres, but i don't know, i have never had the cruise cancel on it's own. maybe a loose connexion?
     
    #5 bisco, Jan 3, 2015
  6. Easy Rider 2

    Easy Rider 2 Senior Member

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    At 70 MPH, if the bump is big enough that you actually classify it as a bump, then it is big enough to cause a momentary ABS/Stability activation.
    More likely to happen if it is on an uphill grade where the engine is pulling a bit.
     
    #6 Easy Rider 2, Jan 4, 2015
  7. R-P

    R-P Active Member

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    They are "Michelin Energy Saver +" 205/55/16's.

    I got them from here, and they claim an A rating in the wet (the "+"version).
    The 'normal' (non "+") version gets points deducted for their behaviour in the wet by the Dutch AAA, but since I have the "+" verson, that is hardly worth mentioning... (still a 3.5 out of 5 rating though).

    As for the uphill bit: I live in Rotterdam, where loads of roads travel under rivers and I think one or two of the instances happened while going uphill out of a tunnel... So very good call if that happens to be it (y)
     
    #7 R-P, Jan 4, 2015
  8. Britprius

    Britprius Senior Member

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    The gen2 Prius cruise control accelerates very hard when it first senses a slight loss of speed on an uphill incline "rather like flooring the throttle". In wet or slippery conditions I find this can easily cause a loss of traction, and cancel cruise control. I use the same size tyres (205/55/16) also with the highest European wet grip rating (A).
    Having had a Mazda in the past "admittedly a manual" on which the reaction rate of the cruise could be set to your own wishes along with the power steering setting. I do find the Prius cruise hard acceleration setting at times alarming in comparison.

    John (Britprius)
     
    #8 Britprius, Jan 4, 2015
    Last edited: Jan 4, 2015
  9. Easy Rider 2

    Easy Rider 2 Senior Member

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    A little moisture on the road will make it more likely, as will running higher than normal tire pressure.
    Something similar can occur when accelerating away from a stop and crossing a damp wide line painted on the road.
     
    #9 Easy Rider 2, Jan 4, 2015
  10. fuzzy1

    fuzzy1 Senior Member

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    If the road is wet enough to cause tire slippage, then safety demands that you not be using cruise control. I quit using CC long before the road is that wet. Traction control cancelling the cruise control is a safety mechanism absent from earlier generation cars.

    Are those tires relatively new, or well worn? How many miles/km on them, or how much tread depth is left? Tires would normally be the first suspect to be checked out, before looking for problems within the traction control.
     
    #10 fuzzy1, Jan 5, 2015
    Last edited: Jan 5, 2015
    Patrick Wong likes this.
  11. R-P

    R-P Active Member

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    Tires are somewhat worn in the front, but not yet to the indicators. Would have to look into how much I drove with them, seems too soon, but they had hardly any thread to start with... Michelin Energy Saver "+". Pressure about 2.6 bar. (Edit just looked up that I drove ~40k km (25k miles) on them and I think the fronts are almost ready for replacement :().

    I tried simulating by setting CC at 100km/h, braking and the restoring at 60km/h so it would automatically accelerate to 100 again while driving over a road that had some repairs done to it (bumpy).
    Couldn't reproduce it.

    And just a few days ago, it cancelled on me again on an incline. Since I drive that stretch very often, I will try again there (it's a drawbridge and probably had some slippery black strips between the bridge and the normal road).

    I just switched to my winter tires shortly after it happening on the bridge this week, so will try to see if they have the same issue.
     
    #11 R-P, Jan 24, 2015
    Last edited: Jan 24, 2015
  12. R-P

    R-P Active Member

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    Update: still happens regularly and haven't pinpointed it to loosing traction.

    Will remove the wintertyres shortly and see if that helps.

    Dealer had no soluton and just looked at me funny while I described the problem.

    Probably mentioned above, but when changing the wheels I will try to tug/push the ABS sensors gently to see if they are secure.
     
    #12 R-P, Mar 31, 2015
  13. CBarr31

    CBarr31 Active Member

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    R-P,

    Here is an old thread about Cruise Control Blinking:

    Cruise control light blinking | PriusChat

    I posted in that one and eventually found that mine was brake related. My pads were worn and after having them replaced and adjusted the problem went away. Could be the brake actuator? Might be something to look at.

    Happy driving,
    Chris
     
    #13 CBarr31, Apr 1, 2015
  14. R-P

    R-P Active Member

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    Still happens and I am sure it is brake-switch related. I can PULL the brake with my toes and cause it to disengage.

    Very wary of removing it as I remember reading on here somewhere you can mess up this switch easily and iirc the brake-light switch and the CC switch are separate. Any good write-ups on how to remove and inspect this switch? (Am searching for this now (hence me landing on my own thread), but open to ideas).

    (EDIT: googling doesn't show the CC brake switche and the brake-light switch to be different, but quite sure I read that somewhere before).
     
    #14 R-P, Jul 4, 2022
    Last edited: Jul 4, 2022
  15. ChapmanF

    ChapmanF Senior Member

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    There is only one switch present at the pedal. On cars with cc, that switch has two sets of contacts, one normally open and one normally closed. The plug connecting to it has more than two wires.

    It's possible a car without cruise from the factory has a different switch there, with only the normally open contacts. Folks adding cruise to old Gen 1s that didn't come with it used to have to replace the switch. Maybe that's what you read?
     
    #15 ChapmanF, Jul 4, 2022
    R-P likes this.
  16. R-P

    R-P Active Member

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    (y) Yeah, while searching today I came across pics of a switch with either 2 or 4 contacts and a DIY youtubevid to add the cruise control. It doesn't seem like it would be easy to open the switch itself, so maybe getting a new one (assuming 30-40€ at Toyota dealer) isn't that bad. But getting it out also doesn't seem that difficult and a quick multimeter measurement might add some clarity to what the actual problem is...
    Always wise to do this days before going on holiday :D (I can still use the other car but that is banned in many Dutch and German cities due to having an Euro3 diesel engine, so despite paying 2500€ 'roadtax', I am not allowed to drive on more and more roads that were payed for by my tax :mad:).
     
    #16 R-P, Jul 4, 2022
  17. R-P

    R-P Active Member

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    New switch ordered. Just drove 1000+ km with the Prius and it's getting pretty annoying :D. Found these two documents in another post and it discusses using a hand-held thing to adjust some sensors (stroke sensor of the brake pedal). imho, if I don't touch those and just swap out the switch (after disconnecting the 12V), it should probably work fine.
    Link-1 adjusting brake pedal
    Link-2 initialization of electronically controlled brake system (may influence the regeneration vs. mechanical brake system??? so sounds like a plan not to mess with it)
     
    #17 R-P, Jul 18, 2022
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